Since the OP did not return with any more information...
This applies to the U.S. and more specially to the areas I am familar with.
Arterial line placement is not part of any Paramedic scope of practice in any state for regular EMS. There have been a few but very few specialty or Flight teams that have sought permission from their state to do that skill for their Paramedics. So yes, it could be part of an expanded scope but to the best of my knowledge, few have included A-line insertion even on CCT or Flight.
If this were to be done in the field by a Paramedic, just like the IV, it would have to be changed once in the hospital. That leaves only one radial artery left to cannulate before looking at the femoral artery.
I also can not see spending much time in the field initiating the line and calibrating the equipment when there are so many other things that need to be done to get the patient to the hospital. I would also not attempt to start an A-line in a moving vehicle in either an ambulance or in a helicopter. Too much damage can be done.
The RNs working with me on the helicopter when I am wearing a Paramedic patch can cannulate the artery if absolutely necessary. However, we may also ask someone at the hospital, especially the RRT, to put in an A-line before or during our arrival. ED physicians may not ahve cannulated an artery since residency. When I am working as an RRT, I can cannulate an artery on IFT, CCT, Specialty and Flight. I can not as a Paramedic. I use whatever device I see appropriate for the age, size and cannulation site requires. We (RRTs, RNs) are trained for different sites with different devices.
The venous femoral line is a central line and although several states do have central lines in their scope of practice, few services will have central line placement in their protocols. The EJ and IO are alternatives and often faster. As well, the field femoral line will have to be replaced with a hospital line that is capable of multiple fluids and for infection control. Of course, they will wait for a stable time for the patient or if at a teaching hospital, one of the residents will establish another line while everyone else is doing other things.
Questions you need to ask:
How many patients do you believe need arterial lines in the field?
Will it make a big difference in your care for prehospital EMS?
How long do you want to stay on scene?
If you are concerned about BP, staying on scene looking for a radial artery to cannulate may not be good use of time for that patient.
Are you going to try both radials and leave the hospital with the opportunity for a radial cannulation?
Do you not have an IO that could work for a line placement if peripheral, including the EJ, is not possible?
Where will you be able to perfect your skills?
